This book reports the work done in preparation of some silver iodide based superionic conductors. It has been divided into five chapters, the first chapter contains general introduction to the work. The second, third, forth and fifth chapters report preparation and ionic conductivity measurements of these materials.The materials studied were prepared by solid state reaction method. X- Ray diffraction analysis was performed for most of the samples to clarify the main structure of the pure compounds and the structural effects of the substitution of one of the ionic component of the system. Ionic conductivity in the temperature range RT–473 K has been measured for all the samples and the effect was discussed. Phase transition temperature variations of these solids were investigated using differential scanning calorimetry (DSC).The measured ionic conductivity comprises contributions from bulk, grain boundary conductivities and electrode polarization effects. To explore extensively these contributions, impedance spectroscopy was done for selected samples at room temperature in the frequency range of 40 Hz–5 MHz.